1. Field of the Invention
The present invention relates to a liquid droplet jetting apparatus which jets liquid droplets.
2. Description of the Related Art
Conventionally, in a liquid droplet jetting apparatus provided with a liquid droplet jetting head for jetting liquid droplets from nozzles, it has been known that a flushing is performed. In the flushing, a certain amount of liquid is usually discharged by consecutively jetting the liquid droplets a plurality of times from the nozzles, for the purpose of, for example, adjusting meniscus of the nozzles or discharging any liquid, the viscosity of which is increased due to drying.
As the liquid droplet jetting apparatus performing the flushing described above, the ink-jet recording apparatuses which jet inks onto recording objective mediums from nozzles to perform recording are disclosed in Japanese Patent Application Laid-Open No. 2008-260172 and Japanese Patent Application Laid-Open No. H10-258531. In order to restore liquid droplet jetting performance of the nozzles, each of the ink-jet recording apparatuses is configured to be capable of performing a so-called suction purge. In the suction purge, a suction operation of a suction pump is performed to discharge inks from the nozzles into a cap member in such a capping state that the cap member comes into close contact with an ink jetting surface of the ink-jet head to cover the nozzles. In the suction purge, a plurality of color inks discharged by the suction purge are mixed one another and then sucked into the nozzles in some cases. For this reason, the flushing is performed after the suction purge to discharge any color mixture inks in the nozzles.
In each of the ink-jet recording apparatuses described in Japanese Patent Application Laid-Open No. 2008-260172 and Japanese Patent Application Laid-Open No. H10-258531, an ink discharge amount (hereinafter referred to as “flushing amount”) in the flushing is not made to be uniform with respect to all the nozzles. The flushing amount is allowed to vary depending on types of inks to be jetted so as to effectively avoid the mixture of the plurality of color inks. In particular, in the ink-jet recording apparatus described in Japanese Patent Application Laid-Open No. 2008-260172, the flushing amount of the nozzles, from which the ink having high specific gravity is jetted, is made to be larger than the flushing amount of the nozzles, from which the ink having low specific gravity is jetted. Further, in the ink-jet recording apparatus described in Japanese Patent Application Laid-Open No. H10-258531, the higher the lightness of ink is, the larger the flushing amount is.
It has been known that, independently of the capping operation during the suction purge, the ink jetting surface is subjected to capping (capped) for protecting the nozzles and preventing the inks in the nozzles from being dried, when the ink jet head is not used (quiescent period of the ink jet head). The capping member used for these purposes is, normally, provided with an atmosphere communication port to prevent the capping member from being deformed and separated from the ink jetting surface and to prevent destruction of meniscus of ink formed in the nozzles, which would be otherwise caused by fluctuation of internal pressure in the cap member resulting from temperature change. An inner space of the capping member is communicated with the atmospheric air via the atmosphere communication port.
Thus, even when the nozzles are covered with the capping member during the quiescent period of the ink-jet head, since the inner space of the capping member is communicated with the atmospheric air, the drying of ink in the nozzles proceeds gradually. Therefore, the flushing (flushing before the use) is performed, immediately before the ink-jet head is started to use so as to discharge the viscosity-increased inks in the nozzles.
However, the present inventors have found out as follows. That is, humidity in the capping member is not uniform and there is humidity distribution in the capping member according to a distance from a suction port. The degree of progress of drying of ink (the degree of increase in viscosity) is varied in a plurality of nozzles according to the humidity distribution. Accordingly, if the flushing amount is made to be equal with respect to the plurality of nozzles, the inks are useless consumed for the nozzles in which the degree of the drying of ink is not severe.
In this regard, Japanese Patent Application Laid-Open No. 2008-260172 and Japanese Patent Application Laid-Open No. H10-258531 describe that the flushing amount is varied, in the flushing performed after the suction purge, according to the types of inks to be jetted. Japanese Patent-Application Laid-Open No. 2008-260172 and Japanese Patent Application Laid-Open No. H10-258531, however, fail to disclose that the flushing amount is varied, during the flushing before the use, according to differences in the degree of progress of the drying of ink among the plurality of nozzles covered with the capping member.